KVM: arm64: Add a range to __pkvm_host_test_clear_young_guest()

In preparation for supporting stage-2 huge mappings for np-guest. Add a
nr_pages argument to the __pkvm_host_test_clear_young_guest hypercall.
This range supports only two values: 1 or PMD_SIZE / PAGE_SIZE (that is
512 on a 4K-pages system).

Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
Link: https://lore.kernel.org/r/20250521124834.1070650-7-vdonnefort@google.com
Signed-off-by: Marc Zyngier <maz@kernel.org>

Author: vdonnefort

arch/arm64/kvm/hyp/include/nvhe/mem_protect.h

@@ -43,8 +43,8 @@ int __pkvm_host_share_guest(u64 pfn, u64 gfn, u64 nr_pages, struct pkvm_hyp_vcpu
 			    enum kvm_pgtable_prot prot);
 int __pkvm_host_unshare_guest(u64 gfn, u64 nr_pages, struct pkvm_hyp_vm *hyp_vm);
 int __pkvm_host_relax_perms_guest(u64 gfn, struct pkvm_hyp_vcpu *vcpu, enum kvm_pgtable_prot prot);
-int __pkvm_host_test_clear_young_guest(u64 gfn, bool mkold, struct pkvm_hyp_vm *vm);
 int __pkvm_host_wrprotect_guest(u64 gfn, u64 nr_pages, struct pkvm_hyp_vm *hyp_vm);
+int __pkvm_host_test_clear_young_guest(u64 gfn, u64 nr_pages, bool mkold, struct pkvm_hyp_vm *vm);
 int __pkvm_host_mkyoung_guest(u64 gfn, struct pkvm_hyp_vcpu *vcpu);
 
 bool addr_is_memory(phys_addr_t phys);

arch/arm64/kvm/hyp/nvhe/hyp-main.c

@@ -331,7 +331,8 @@ static void handle___pkvm_host_test_clear_young_guest(struct kvm_cpu_context *ho
 {
 	DECLARE_REG(pkvm_handle_t, handle, host_ctxt, 1);
 	DECLARE_REG(u64, gfn, host_ctxt, 2);
-	DECLARE_REG(bool, mkold, host_ctxt, 3);
+	DECLARE_REG(u64, nr_pages, host_ctxt, 3);
+	DECLARE_REG(bool, mkold, host_ctxt, 4);
 	struct pkvm_hyp_vm *hyp_vm;
 	int ret = -EINVAL;
 
@@ -342,7 +343,7 @@ static void handle___pkvm_host_test_clear_young_guest(struct kvm_cpu_context *ho
 	if (!hyp_vm)
 		goto out;
 
-	ret = __pkvm_host_test_clear_young_guest(gfn, mkold, hyp_vm);
+	ret = __pkvm_host_test_clear_young_guest(gfn, nr_pages, mkold, hyp_vm);
 	put_pkvm_hyp_vm(hyp_vm);
 out:
 	cpu_reg(host_ctxt, 1) = ret;

arch/arm64/kvm/hyp/nvhe/mem_protect.c

@@ -1111,17 +1111,21 @@ int __pkvm_host_wrprotect_guest(u64 gfn, u64 nr_pages, struct pkvm_hyp_vm *vm)
 	return ret;
 }
 
-int __pkvm_host_test_clear_young_guest(u64 gfn, bool mkold, struct pkvm_hyp_vm *vm)
+int __pkvm_host_test_clear_young_guest(u64 gfn, u64 nr_pages, bool mkold, struct pkvm_hyp_vm *vm)
 {
-	u64 ipa = hyp_pfn_to_phys(gfn);
+	u64 size, ipa = hyp_pfn_to_phys(gfn);
 	int ret;
 
 	if (pkvm_hyp_vm_is_protected(vm))
 		return -EPERM;
 
-	assert_host_shared_guest(vm, ipa, PAGE_SIZE);
+	ret = __guest_check_transition_size(0, ipa, nr_pages, &size);
+	if (ret)
+		return ret;
+
+	assert_host_shared_guest(vm, ipa, size);
 	guest_lock_component(vm);
-	ret = kvm_pgtable_stage2_test_clear_young(&vm->pgt, ipa, PAGE_SIZE, mkold);
+	ret = kvm_pgtable_stage2_test_clear_young(&vm->pgt, ipa, size, mkold);
 	guest_unlock_component(vm);
 
 	return ret;

arch/arm64/kvm/pkvm.c

@@ -439,7 +439,7 @@ bool pkvm_pgtable_stage2_test_clear_young(struct kvm_pgtable *pgt, u64 addr, u64
 	lockdep_assert_held(&kvm->mmu_lock);
 	for_each_mapping_in_range_safe(pgt, addr, addr + size, mapping)
 		young |= kvm_call_hyp_nvhe(__pkvm_host_test_clear_young_guest, handle, mapping->gfn,
-					   mkold);
+					   1, mkold);
 
 	return young;
 }